1. Field of the Invention
The present invention relates to a saddle adjusting technology, and more particularly to a saddle adjusting device for a folding bicycle which can offer a multi-height adjusting and assuredly-fixing function.
2. Description of the Prior Art
Common bicycle saddles are all disposed on a top end of a seat post which is inserted into a bicycle frame, and the bicycle frame is provided with a seat post clamp for clamping the seat post to fix the seat post.
When the height of the saddle needs adjusting, the seat post clamp should unclamp the seat post first, and then the height of the seat post which protrudes out of the bicycle frame can be adjusted, and finally after the saddle is adjusted to a desired height, the seat post clamp will clamp the seat post again to fix the seat post on the bicycle frame.
However, the existing bicycle frames have various styles, and it is particularly so for the folding bicycles, because the folding bicycles must consider the volume after being folded so as to facilitate the carrying, therefore, there are many different forms of frames.
Referring to FIG. 1, a conventional triangular bicycle frame 8 essentially comprises a front post 81, a seat post 82 and a bottom post 83 that are pivotally connected to one another. The top end of the seat post 82 is pivotally connected to the top end of the front post 81, and the bottom end of the seat post 82 is pivotally connected to a rear wheel 84 and a rear end of the bottom post 83 while the front end of the bottom post 83 is fastened on a fastening seat 811 on a lower portion of the front post 81. The bottom end of the front post 81 is connected with a front fork 812 to be pivoted to the front wheel 85. The top end of the front post 81 is provided with a handlebar 86, and the middle portion of the bottom post 83 is provided with a chain ring 87 having a pair of cranks 88 and a pair of pedals 881. The chain ring 87 is drivingly connected to a smaller chain ring 89 disposed on the rear wheel 84 through a belt 871. The seat post 82 is further provided with a saddle mechanism 9. By such arrangements, a folding bicycle is formed.
The saddle mechanism 9 includes a seat body 91 which is slightly L-shaped and slidably engaged on the seat post 82. The top end of the seat body 91 is provided with a saddle 92.
When no external force is applied between the seat body 91 and the seat post 82, the seat body 91 and the seat post 82 are in loose fit state. The seat body 91 is provided with two seat post clamps 93 for clamping the seat body 91 on the seat post 82. The seat post 82 is provided with a bolt 94 having one end protruded out of the seat post 82, and the seat body 91 is defined with plural engaging grooves 95 correspondingly to the bolt 94. When the two seat post clamps 93 are loosened, the respective engaging grooves 95 will form clearances for insertion of the bolt 94, and when the two seat post clamps 93 are tightened, the engaging grooves 95 will be forced to clamp the bolt 94 fixedly.
In other words, the saddle mechanism 9 can be positioned at a desired position through the cooperation of the bolt 94 with the engaging grooves 95, and the seat body 91 is clamped on the seat post 82 by the two seat post clamps 93, thus realizing the position adjustment and fixing of the seat body 91.
Nevertheless, considering the lightness and the cost of the saddle mechanism 9, the above seat body 91 is made of engineering plastic, but the engineering plastic is still not rigid enough even it has a high strength, so that when the seat body 91 is clamped on the seat post 82 by the seat post clamps 93, the engineering-plastic-made seat body 91 itself will be compressed to cause elastic deformation. Therefore, the resulting clamping force is less than the clamping force applied by the conventional metal frame to the metal seat post, that is to say, when the seat body 91 bears the weight of the rider, the seat body 91 clamped by the two seat body clamps 93 will still slip slightly.
Commonly, a clearance difference between a loosened seat post clamp and a tightened seat post clamp is only about 1 to 2 mm, but the changing of the clearance must allow the engaging grooves 95 to define a clearance therebetween for passage of the bolt 94, so that the engaging portion of the engaging groove 95 for the bolt 94 only has a depth of 1-2 mm. Further since the bolt 94 is cylinder-shaped, the contact area between the engaging groove 95 and the bolt 94 is quite limited, and since the seat body 91 is made of the engineering plastic, when the seat body 91 bears the weight of the rider and slides relative to the seat post 82, the bolt 94 will be forced to disengage from the engaging groove 95, thus defeating the positioning effect. If such a situation occurs frequently, the engaging groove 95 will be damaged to cause permanent deformation, thus losing the positioning effect.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.